Mercede Johnston, the opinionated sister of Bristol Palin‘s baby daddy Levi Johnston, believes Sarah Palin would have had a “mental breakdown” if she were elected president — and says that Bristol told her brother, “I prayed you weren’t the father,” after she became pregnant.

Mercede posed nude for the September issue of Playboy and gave an equally revealing interview to George Gurley. Asked what kind of president Sarah Palin would be, she responded: “I think she’d have had a mental breakdown . . . As governor she quit on us. What does that say about her?” When Gurley asked what percentage of Wasilla residents “can’t stand Palin,” Mercede responded, “I would say 70 percent.”

Mercede also claims the Palins are so polarizing in the small Alaskan town that she can’t work. “It’s hard to get a job in this town because of the Palins,” she tells Playboy, adding, “People say, ‘Oh, Mercede Johnston, I don’t know if people are going to come in if she works here.’ ”

Regarding Bristol’s relationship with Levi, she claims Bristol sent a text message to Levi after she found out she was expecting son Tripp that read, “Ever since the moment I found out I was pregnant, I prayed to God you weren’t the father.”

Mercede — who had claimed on her blog that “Levi never liked [Bristol] to drink since it just made her more promiscuous” — also told Gurley that Bristol, who’s since become an advocate for teen abstinence, wanted to get pregnant: “Bristol’s pregnancy wasn’t . . . an accident. She and Levi planned it. They were trying to conceive for months.”

Mercede also tells Playboy that Track Palin, Sarah’s 22-year-old son who is an Army reservist, used drugs. She claims, “He did OxyContin and mostly cocaine. He didn’t choose to go into the Army; he went there because his mom made him, to get him out of the way so when she was at the convention they wouldn’t know he does drugs and would think he was a patriot.” A Palin family rep declined to comment.